import java.util.Scanner;

public class Test {
    public static int fib(int n){
        if(n==1||n==2){
            return 1;
        }
        else {
            return fib(n-1) + fib(n-2);
        }
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x = sc.nextInt();
        int ret = fib(x);
        System.out.println(ret);
    }
}
